EP1913044A2

EP1913044A2 - Method for preparing a polymeric material including a multiblock copolymer prepared by controlled free-radical polymerisation

Info

Publication number: EP1913044A2
Application number: EP06794532A
Authority: EP
Inventors: Olivier Guerret
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2005-08-09
Filing date: 2006-08-08
Publication date: 2008-04-23
Also published as: US20100168338A1; WO2007017614A2; FR2889703A1; JP2009504830A; CN101365732A; WO2007017614A3

Abstract

A method for preparing a polymeric material including a multiblock copolymer with n blocks, where n is an integer no lower than 2, which method comprises at least one cycle of steps including (a) a step of synthesising a block by performing controlled free-radical polymerisation of one or more free-radical polymerisable monomers, and (b) a step of polymerising the monomers that were not converted during step (a) into a polymer having a number-average molecular weight lower than the number-average molecular weight of said block, wherein said cycle of steps is carried out at least for the (n-1) first blocks.

Description

PROCESS FOR THE PREPARATION OF A POLYMERIC MATERIAL

COMPRISING A MULTIBLOC COPOLYMER OBTAINED BY

CONTROLLED RADICAL POLYMERIZATION

DESCRIPTION

TECHNICAL AREA

The present invention relates to a process for preparing a polymeric material comprising a multiblock copolymer obtained by controlled radical polymerization.

The present invention also relates to a nanostructuring and nanostructured polymeric material which can be used as a thermoplastic material or as a reinforcing additive or rheological additive of host matrices, this material being able to find its application in the manufacture of transparent parts having improved mechanical properties. .

The general field of the invention is therefore that of polymeric materials, and more particularly nanostructured polymeric materials.

Nanostructured polymeric materials are materials organized into domains with dimensions smaller than 100 nm. Such materials have the advantage of remaining transparent and, in case of introduction of said material into a host matrix, not to disturb the properties thereof. STATE OF THE ART

The nanostructured domains can be produced by polymer particles dispersed in another polymer constituting a host matrix, said particles having a size defining the size of the domains. These particles are obtained by an emulsion polymerization process. However, it turns out that it is difficult, on an industrial scale, to obtain, to this day, by this process particles of such sizes because of the instability of the emulsions. In addition, the particle distribution is strongly conditioned by the mixing step, which, if not carried out carefully, may hinder the final physicochemical properties.

To obtain nanometric distributions of a polymer in a host matrix, some authors have used the concept of self-organization of block copolymers. Thus, if an AB block copolymer is mixed with a polymer C compatible with the block B, the resulting mixture is organized because of the repulsions between the block A and the mixture of the block B with the block C. These repulsions take place at the scale of polymer chains, which leads to organizations on the scale of a few tens of nanometers.

The advantage of this nanostructured material manufacturing approach lies in the fact that the mixture is organized thermodynamically stable, which makes manufacturing much less dependent on the mixing process.

Block copolymers are generally obtained by so-called living polymerization techniques, that is to say techniques where termination reactions tend to be limited, so that the polymer chains continue to grow as long as they occur. Monomers remain available.

Two major routes of synthesis of living polymerization predominate:

anionic polymerization, dedicated to the synthesis of copolymers from ethylenic monomers comprising one or more electroattractive substituents, such as a copolymer of the polystyrene-butadiene type;

cationic polymerization, dedicated to the synthesis of copolymers from ethylenic monomers comprising one or more electron-donor substituents, such as copolymers of the polyether type.

However, these two synthetic routes are dependent, as is apparent from the above paragraphs, on the nature of the monomers and therefore limit the variety of monomers that can be used in the copolymer blocks and therefore the fields of application of these synthetic routes for to manufacture nanostructured materials and, consequently, materials obtained.

For about twenty years, scientists have worked to expand the possibilities of synthesis of block copolymers by developing a new synthetic route, which is the radical polymerization, more particularly the controlled radical polymerization (known by the abbreviation PRC).

Several types of controlled radical polymerization exist depending on the nature of the control agent used:

the type used as nitroxide control agent and, for example, as initiator of alkoxyamines, known by the abbreviation SFRP (corresponding to the English terminology "Stable free radical polymerization");

the type using as control agent metal complexes and, for example, as an initiator of halogenated compounds, known under the abbreviation ATRP (corresponding to the English terminology "Atom Transfer Radical Polymerization");

the type using sulfur compounds as a control agent (also fulfilling the role of initiators) such as dithioesters, trithiocarbamates, xanthates, dithiocarbamates, known under the abbreviation RAFT (corresponding to the terminology "Reversible Addition Fragmentation" Transfer ").

The role of the control agent is to slow the biradical termination reactions so as to favor the growth of the chains by addition to free monomer. However, when one tries to push these polymerizations towards high Conversions, termination reactions necessarily take place. Gradually decreasing the ratio between propagating chains and control agent considerably slows down the kinetics of polymerization.

Thus, with the SFRP or ATRP technique, to go beyond a conversion rate of 90%, it is generally necessary to wait more than 24 hours.

It is thus easily apparent that controlled radical polymerization, while allowing the production of polymers of a broader chemical nature compared to ionic polymerizations, presents serious limitations for the synthesis of block copolymers in an industrial environment. To overcome these limitations, it is for example possible to stop the polymerization of a block at a chosen conversion rate and to eliminate, for example, by evaporation, the residual amount of monomers, before the synthesis of the subsequent block before attach to the previous block. The step of removing the residual quantity of monomers is a heavy step, insofar as it takes place in a viscous medium and therefore requires the use of either expensive industrial equipment (such as an extruder ) or at unacceptable distillation times in the industrial environment.

To overcome the limitations mentioned above, it is also conceivable to carry out the polymerization of the subsequent block in the presence of the monomers not converted in the previous block and to ensure removal of the residual monomers at the result of the synthesis of the block copolymer. This alternative, however, causes a subsequent block pollution with the monomers of the previous block, which leads to a subsequent block having a denaturation of its properties, in particular the physicochemical properties, compared to a "pure" block, it is that is, not including any monomers other than those to be formed. Thus, when it is desired to associate a first block (called block A, comprising monomers Mi) with a low glass transition temperature (Tg ₁ ) with a second block (called block B, comprising monomers M ₂ ) with a high temperature of glass transition (Tg ₂ ), the glass transition temperature of the second block is governed by the law of Fox defined by the following equation:

1 / Tg (B) = x (M ₁ ) / T _{g 1} + x (M ₂ ) / T ₂

in which: X (M ₁ ) and x (M ₂ ) respectively represent the volume fraction of M ₁ and the volume fraction of

M ₂ with x (M ₁ ) + x (M ₂ ) = 1;

Tg ₁ corresponds to the glass transition temperature of the first block; - Tg ₂ corresponds to the glass transition temperature of the second block.

It can easily be seen that the glass transition temperature of the second block is affected by the presence of monomers from the first block. This results in a deterioration of physico-chemical and mechanical properties compared to what one would expect from a pure diblock polymer.

Thus, the known preparation processes for block copolymers (or multiblocks) by controlled radical polymerization all have one or more of the following disadvantages:

they require heavy treatment steps to eliminate or reduce between the synthetic steps of each block, the residual monomers;

- They cause a pollution of the blocks by the constituent monomers of the previous blocks, which causes a change in the physico-chemical and mechanical properties of the resulting multiblock copolymers compared to what one would expect with a pure multiblock copolymer.

The inventors have therefore set themselves the objective of developing a process for preparing a polymeric material comprising a multiblock copolymer which does not have the drawbacks of the processes of the prior art mentioned above. They have discovered, surprisingly, that by performing a particular step after the blocking step, it was possible to overcome the above mentioned disadvantages.

STATEMENT OF THE INVENTION

The invention thus relates, according to a first object, to a process for preparing a polymeric material comprising a multiblock copolymer comprising n blocks, n being an integer greater than or equal to 2, said method comprising at least one cycle of steps comprising:

a) a step of synthesizing a block by controlled radical polymerization of one or more radically polymerizable monomers; b) a polymerization step of the monomers not converted in step a) into a polymer having a number average molecular weight less than the number average molecular weight of said block; said cycle of steps being performed at least for the

(n-1) first blocks. Advantageously, the cycle of steps is performed for the n blocks.

Thus, thanks to the polymerization step b), the monomers that are not converted during each step a) are converted into a polymer having a number-average molecular mass less than the number-average molecular mass of said block, of identical chemical nature. block audit. The polymer produced is thus compatible with the block produced previously.

By "polymer compatible with the block" is meant a polymer capable of interacting with said block, so as to be miscible in said block.

Thus, it eliminates the residual monomer removal step and the risk of polluting subsequent blocks. At the end of the process the invention thus provides a nanostructured and nanostructured polymeric material having physicochemical and mechanical properties, such as the glass transition temperature, inherent to each block, unaltered compared to those of a pure block.

This method also proves to be an easy and inexpensive implementation method and therefore very advantageous for use in an industrial environment.

In other words, the preparation method of the invention comprises successively: a step of preparing a first block from one or more monomers by controlled radical polymerization;

a step of polymerization of the monomers that are not converted during the preceding step into a polymer of chemical nature identical to the first block but having a number-average molecular mass smaller than the number-average molecular mass of the first block; a step of introducing a second monomer or mixture of monomers, different from the monomer or mixture of monomers used to produce the first block; a polymerization step of the second monomer or monomer mixture to form the second block;

a step of polymerization of the monomers not converted during the previous step into a polymer of a chemical nature identical to the second block but having a number average molecular weight smaller than the number-average molecular mass of the second block and so on, up to the number of blocks desired for the copolymer, being extended that the third, ..., nth blocks may be of a nature identical or different from that of the first and second blocks.

Although the invention relates to a method for preparing a polymeric material comprising a multiblock copolymer, it is particularly applicable to the preparation of a polymeric material comprising a copolymer comprising at least one block A and at least one block B.

The application therefore also relates to a process for preparing a polymeric material comprising a copolymer comprising at least one block A and at least one block B, said process comprising successively:

1) a polymerization step of one or more monomers radically polymerizable by controlled radical polymerization, to form the block A;

2) a step of polymerization of the residual monomer or monomers not converted during step 1), to form a polymer of chemical nature identical to the block A but of number average molecular mass less than that of the block A and, generally, polydispersity index higher than that of block A; 3) a step of adding to the medium resulting from the previous steps 1) and 2) of one or more radically polymerizable monomers precursors of block B;

4) a step of polymerization of said precursor monomer or monomers of block B by controlled radical polymerization, said block B being bonded to block A by covalent bonding;

5) optionally a step of polymerization of the residual monomer or monomers not converted during step 4), to form a polymer of chemical nature identical to block B but of number average molecular weight less than that of block B and, generally , of polydispersity index greater than that of block B.

It is understood that the invention applies not only to the synthesis of diblock copolymers, but also triblock copolymers, multi-branched copolymers, etc.

The synthesis of the blocks of the multiblock copolymers of the invention is carried out by controlled radical polymerization at a temperature appropriate to the type of PRC chosen (according to whether it is SFRP, ATRP or RAFT) and to the type of monomers chosen.

Advantageously, the radical polymerization technique used for each step a) or for steps 1) and 4) is the SFRP polymerization preferably carried out in the presence of at least one alkoxyamine, this type of compound ensuring, at the same time, the role of initiating agent and controlling agent. Alkoxyamines advantageously used according to the invention may be chosen from the monoalkoxyamines of formula (I):

(I) in which:

R 1 and R ₃ , which may be identical or different, represent a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 3; R.2 represents a hydrogen atom, an alkali metal, such as Li, Na, K, an ammonium ion such as NH ₄ ⁺ , NBu ₄ ⁺ , NHBU ₃ ^"1" , a linear or branched alkyl group, having a number of carbon atoms ranging from 1 to 8, a phenyl group.

A particular example of monoalkoxyamine is that corresponding to the following formula:

Alkoxyamines which can advantageously be used according to the invention may also be polyalkoxyamines resulting from a process comprising reacting one or more alkoxyamines of the following formula (I):

Ri C (CH ₃ ) ₃

R ₃ -CON CH-C (CH ₃ ) ₃

C (O) OR ₂ P (O) (OEt) ₂ (D in which:

R 1 and R ₃ , which may be identical or different, represent a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 3;

R.2 representing a hydrogen atom, a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 8, a phenyl group, an alkali metal such as Li, Na, K, an ion ammonium such as NH ₄ ⁺ , NHBU ₃ ⁺ ; preferably, R 1 being CH ₃ and R 2 being H; with at least one polyunsaturated compound of formula (II):

(II) wherein Z represents an aryl group or a group of formula in which Zi represents a polyfunctional structure derived for example from a polyol compound, X is an oxygen atom, a nitrogen atom carrying a carbon group or an oxygen atom, a sulfur atom and n is an integer greater than or equal to 2, in the presence or absence of solvent (s), preferably chosen from alcohols such as ethanol, aromatic solvents, chlorinated solvents, aprotic polar ethers and solvents, at a temperature ranging, in general, from at 90 ^° C., preferably from 25 ° to 80 ^° C., the molar ratio between monalcoxyamine (s) of formula (I) and polyunsaturated compound (s) of formula (II) ranging from 1.5 to 1.5n preferably from n to 1.25 n, this step possibly being followed by a step of evaporation of the possible solvent (s).

The polyunsaturated compound of formula (II) may be chosen from polyfunctional vinylbenzenes (Z being then an aryl group) or from polyfunctional acrylic derivatives (Z being then a group of formula Zi- [XC (O) J _n ) - Preferably the polyunsaturated compound is divinylbenzene, trivinylbenzene, ethylene glycol diacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, cyclohexane dimethanol diacrylate diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylates (sold by Sartomer under the names SR259, SR344, SR610) and hexanediol diacrylate alkoxylates (marketed by Sartomer). under the names CD561, CD564, CD560), bisphenol-A diacrylate, ethoxylated bisphenol-A diacrylate (sold by Sartomer under the names SR 349, SR601, SR602, CD9038), trimethylolpropane triacrylate, pentaerythritol triacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate (sold by Sartomer under the names SR454, SR499, SR502, SR9035, SR415), propoxylated glyceryl triacrylate (sold by Sartomer under the name SR9020), propoxylated trimethylolpropane triacrylate (sold by Sartomer under the names SR492 and CD501), pentaerythritol tetraacrylate, di-trimethylolpropane tetracrylate, pentaerythritol tetraacrylate ethoxylated

(sold by Sartomer under the name SR494), dipentaerythritol pentacrylate, modified caprolactones dipentaerythritol hexaacrylate

(marketed by Sartomer under the names

Kayarad DCPA20 and DCPA60), dipentaerythritol polyacrylate (marketed by UCB Chemicals under the name DPHPA).

The polyalkoxyamines thus produced have the following formula (III):

(III)

in which n, Ri, R ₂ and R ₃ , Z have the same meanings as those given above.

A particular example of polyalkoxyamine according to the general definition given above is polyalkoxyamine corresponding to the following formula:

Without the plaintiff being held to any explanation, she thinks that, in the case where the polymerization proceeds in emulsion, the alkoxyamines of formula (I) and / or the polyalkoxyamines of formula (III) play both the role of initiator (and control agent) and emulsifier agent; thus, the surfactant properties of the water-soluble alkoxyamines of formula (I) and / or polyalkoxyamines of formula (III) make it possible to moderate or even to avoid the use of other surfactants.

In particular, the alkoxyamines of formula (I) and / or the polyalkoxyamines of formula (III) are water-soluble.

For the purposes of the present invention, the term "water-soluble alkoxyamine" or "water-soluble polyalkoxyamine" means any alkoxyamine of formula (I) or polyalkoxyamine of formula (III) whose solubility in the water phase or (water / water-miscible compound) is from minus 1 g / 1 at 25 ^° C.

The alkoxyamine or polyalkoxyamine may be introduced into the polymerization medium (i.e., during each step a) or steps 1) and 4) at a rate of from 0.01% to 10%, preferably 0.1 to 5% by weight relative to the mass of monomer (s).

By monomer is meant any monomer polymerizable or copolymerisable radical. The term monomer covers, of course, mixtures of several monomers. The monomers used for producing the blocks may be chosen from monomers having a carbon-carbon double bond capable of radical polymerization, such as vinyl, vinylidene, diene and olefinic, allylic, acrylic, methacrylic monomers, and the like.

The monomers used can in particular be chosen from vinylaromatic monomers such as styrene or substituted styrenes, especially α-methylstyrene and sodium styrene sulphonate, dienes such as butadiene or isoprene, and acrylic monomers such as acrylic acid or its salts, alkyl, cycloalkyl or aryl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, ethylhexyl acrylate or phenyl acrylate, hydroxyalkyl acrylates such as acrylate 2-hydroxyethyl acrylates, ether alkyl acrylates such as 2-methoxyethyl acrylate, alkoxy- or aryloxypolyalkyleneglycol acrylates such as methoxypolyethylene glycol acrylates, ethoxypolyethylene glycol acrylates, methoxypolypropylene glycol acrylates, acrylates and the like. methoxy-polyethylene glycol-polypropylene glycol or mixtures thereof, aminoalkyl acrylates such as 2- (dimethylamino) ethyl acrylate (ADAME), amino salt acrylates such as [2- (acryloyloxy) ethyl] trimethylammonium chloride or sulfate or [2- (acryloyloxy) ethyl] dimethylbenzylammonium chloride or sulfate, fluorinated acrylates, silyl acrylates, acrylates phosphors such as alkylene glycol phosphate acrylates, methacrylic monomers such as methacrylic acid or its salts, alkyl, cycloalkyl, alkenyl or aryl methacrylates such as methyl methacrylate, lauryl methacrylate, cyclohexyl, allyl or phenyl, hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate, ether alkyl methacrylates such as 2-ethoxyethyl methacrylate, alkoxy methacrylates, or aryloxy-polyalkylene glycol such as methoxypolyethylene glycol methacrylates, ethoxypolyethylene glycol methacrylates, methoxypolypropylene glycol methacrylates, methoxy-polyethylene glycol-polypropylene glycol methacrylates or mixtures thereof, aminoalkyl methacrylates such as 2- (dimethylamino) ethyl methacrylate (MADAME), amine salt methacrylates such as chloride or sulfate of [ 2- (methacryloyloxy) ethyl] trimethylammonium or [2- (methacryloyloxy) ethyl] dimethylbenzylammonium chloride or sulfate, fluorinated methacrylates such as 2,2,2-trifluoroethyl methacrylate, silylated methacrylates such as 3- methacryloylpropyltrimethylsilane, phosphorus methacrylates such as alkylene glycol phosphate methacrylates, hydroxyethylimidazolidone methacrylate, hydroxyethylimidazolidinone methacrylate, 2- (2-oxo-1-imidazolidinyl) ethyl methacrylate, acrylonitrile , acrylamide or substituted acrylamides, 4-acryloylmorpholine, N-methylolacrylamide, acrylamidopropyltrimethylartitanium (APTAC) chloride, acrylamidomethylpropanesulfonic acid (AMPS) or its salts, methacrylamide or substituted methacrylamides, N-methylolmethacrylamide, methacrylamidopropyltrimethylammonium chloride ( MAPTAC), itaconic acid, maleic acid or its salts, maleic anhydride, alkyl or alkoxy- or aryloxy-polyalkyleneglycol maleates or hemimaleate, vinylpyridine, vinylpyrrolidinone, (alkoxy) poly ( alkylene glycol) vinyl ether or divinyl ether, such as methoxy poly (ethylene glycol) vinyl ether, poly (ethylene glycol) divinyl ether, olefinic monomers, among which mention may be made of ethylene, butene, hexene and 1-octene as well as fluorinated olefinic monomers, and vinylidene monomers, among which mention may be made of vinylidene fluoride, alone or as a mixture of at least two aforementioned monomers.

It is possible to add to the polymerization medium for each step a) or for steps 1) and 4), when the polymerization takes place in emulsion, at least one emulsifying agent, that is to say a surfactant allowing ^f stabilize the emulsion, provided that said emulsifying agent is not an alkoxyamine as defined above. All usual emulsifier in this type of emulsion can be used ^f.

The emulsifying agent may be anionic, cationic or nonionic. The emulsifying agent may be an amphoteric or quaternary or fluorinated surfactant. It may be chosen from alkyl or aryl sulphates, alkyl or aryl sulphonates, fatty acid salts, polyvinyl alcohols and polyethoxylated fatty alcohols. By way of example, the emulsifying agent can be chosen from the following list:

sodium lauryl sulphate,

sodium dodecylbenzenesulphonate,

- sodium stearate,

- nonylphenolpolyethoxylated, - sodium dihexylsulfosuccinate,

sodium dioctylsulfosuccinate,

- lauryl dimethyl ammonium bromide,

- lauryl amido betaine,

perfluoro octyl potassium acetate. The emulsifying agent may also be an amphiphilic block or random or graft copolymer, such as copolymers of sodium styrene sulphonate and in particular sodium polystyrene-b-poly (sodium styrene sulphonate) or any amphiphilic copolymer prepared by any other polymerization.

The emulsifying agent may be introduced into the polymerization medium in a proportion of 0.1% to 10% by weight relative to the mass of monomer (s).

The polymerization steps for producing the blocks (steps a) and steps 1 and 4) are performed at a temperature appropriate to the type of monomers used in the constitution of the block.

The polymerization temperatures depend on the constituent monomers of the block. Thus, to initiate the polymerization of acrylate monomers from alkoxyamines as defined above, is advantageously chosen a temperature greater than 50 ^° C., preferably less than 130 ^° C., more preferably ranging from 90 ^° C. to 125 ^° C. For initiating the polymerization of methacrylate monomers with Starting from alkoxyamines as defined above, a temperature of greater than 50 ^° C., preferably less than 200 ° C., is preferably chosen, preferably ranging from 90 ^° C. to 175 ^° C. The blocks obtained according to the process of the invention. The invention generally has a number average molecular weight of from 1000 to ⁶ g / mol and a polydispersity index of less than 2.

The degree of conversion of the monomers or monomer mixture constituting the blocks generally depends on the manufacturing time devoted to the block and is generally set so as to obtain a block of average molar mass in predetermined number.

According to the invention, between two steps of preparation of two adjacent blocks (that is to say between two steps a) of two successive cycles or between steps 1) and 4)) and possibly after the step of preparation of last block (that is to say the end block) (corresponding to steps a) of two successive cycles or in step 5)), there is provided a polymerization step of the monomer (s) unconverted (s) constituent of the block which has just been synthesized. This polymerization is carried out, for each step b) or for steps 2) and 5), generally by so-called conventional radical polymerization, namely by adding to the medium in which the block has just been produced, a so-called conventional radical polymerization initiator chosen, generally, from the peroxide compounds (such as a peroxide compound of the Luperox ™ range, the persulfate compounds (such as sodium persulfate, potassium persulfate, ammonium persulfate), azo compounds (such as bis-azidoisobutyronitrile, titled AiBN, 2,2'-azobis (2-amidinopropane) dihydrochloride and the metal and ammoniacal salts of 4, 4'-azobis (4-cyanopentanoic acid)), redox compounds (such as the persulfate (sodium, potassium or ammonium / vitamin C) pair, the persulfate / metabisulphite pair of sodium or potassium, the water pair Oxygenated / ferrous ion salts, tert-butyl hydroperoxide / sodium sulfoxylate pair as well as any other possible oxidant (s) / reductant (s) combination.) The polymerization temperature of this step (i.e. for each either b) or for steps 2) and 5)) is preferably chosen so as to be at least 20 ^° C. lower than that for polymerization of the block which has just been polymerized (ie say in steps a) or steps 1) and 4)). The fact of decreasing the temperature makes it possible to preserve the block previously synthesized in the form of a living polymer, without however continuing the polymerization thereof.

The polymer obtained after steps b) or steps 2) and optionally 5) has a number average molecular weight less than that of the block synthesized just before and, generally, also a polydispersity index greater than that of the synthesized block just before. The condition on the number average molecular weight is essential for the final resulting material (polymer blocks + polymers resulting from the polymerization of the unconverted monomers of each of the blocks) to be nanostructuring, these conditions allowing the polymers produced by conventional radical polymerization to remain compatible with block copolymer blocks produced by controlled radical polymerization.

To facilitate obtaining this condition on the number average molecular weight, it may be advantageous to add, for each step b) or for steps 2) and 5), a transfer agent (i.e. an agent capable of regulating the molecular weight of the polymer chains produced), this transfer agent possibly being chosen from: sulfur compounds, for example mercaptan compounds comprising at least 4 carbon atoms, such as butane mercaptan, dodecyl mercaptan, terdodecyl mercaptan, disulfide compounds;

- Alcohol compounds, for example, hindered phenols such as tertbutyl catechol, secondary alcohols such as isopropanol;

transfer agents used for radical polymerization of the RAFT type, such as trithiocarbonates (in particular dibenzyltrithiocarbonate), xanthates, dithioesters, dithiocarbamates. It may also be provided, so that the polymers produced in these steps have particular properties, to add, in addition to the polymerization initiator, monomers different from those of unconverted monomers.

Thus, the method of the invention makes it possible to obtain a polymeric material comprising a multiblock copolymer comprising n blocks connected to each other by a covalent bond, n being an integer greater than or equal to 2, and for at least each of ( n-1) first blocks, polymer chains formed by unconverted monomers forming part of the corresponding block, said chains having a number average molecular weight less than that of the corresponding block and, generally, a polydispersity index greater than that of the corresponding block.

As mentioned above, this process is particularly suitable for the preparation of a polymeric material comprising a diblock copolymer A-B, such as a copolymer (n-butyl acrylate / methyl methacrylate).

In this case, as the progress of the process progresses, one obtains respectively for a polymeric material comprising at least one diblock copolymer AB: after the first step, a mixture comprising preamble polymer chains prefiguring Block A of the block copolymer and unconverted monomers; after the second step, a mixture comprising the rebootable polymer chains of the first step and polymer chains resulting from the polymerization of the unconverted monomers of the first step; after the fourth step, a mixture comprising the diblock copolymer consisting of block A and block B linked together by covalent bonding, polymer chains resulting from the polymerization of the unconverted monomers of the first stage, monomers that are not converted during the course of the fourth step; after the fifth step, a mixture comprising the AB diblock copolymer, polymer chains resulting from the polymerization of the residual monomers of the first step and polymer chains resulting from the polymerization of the unconverted monomers during the fourth step.

Insofar as the number-average molecular weight of the polymer chains resulting from the polymerization of the residual monomers of the first step is less than that of the block A, the said chains are compatible with the block A. The chains resulting from the fifth step, because of their number average molecular weight, are either compatible with the block B, or it is the block B which is compatible with these chains. The method of the invention therefore leads to a nanostructuring and nanostructured material. The conditions for carrying out the process for preparing a polymeric material comprising an AB diblock copolymer are similar to those already described in the general part relating to materials comprising a multiblock copolymer.

More precisely, the advantageous operating conditions as well as the advantageous characteristics of the products resulting from the first step (step 1) can be the following ones:

an SFRP type polymerization for the synthesis of the first block, preferably using as initiator alkoxyamines or polyalkoxyamines as defined above;

monomers used for the synthesis of the first block, chosen from acrylic and methacrylic derivatives, styrene derivatives as defined above; a polymerization temperature greater than 50 ^° C. and less than 130 ^° C., preferably ranging from 90 ^° C. to 125 ^° C.; a conversion achieved, preferably, ranging from 60% to 95%, more preferably ranging from 65 to 90%;

a number-average molecular mass of the first block, preferably ranging from 5000 g / mol to 500000 g / mol. The advantageous operating conditions of the second step (step 2) can be as follows:

the use for polymerization of unconverted monomers of conventional initiators chosen from azo derivatives such as bis-azido-isobutyronitrile (AIBN), peroxides from the Luperox ™ range, redox couples such as a peroxide-associating Fenton system; from hydrogen to a metal (iron or copper) or such as the persulfate / bisulphite pair;

a polymerization temperature ranging from 30 ^° C. to 100 ^° C., preferably from 50 ° C. to 80 ^° C .; the presence of transfer agents for regulating the molecular mass of the chains produced during this step, said agents being preferably chosen from mercaptan compounds having at least 4 carbon atoms, such as butane mercaptan and dodecyl mercaptan, terdodecyl mercaptan, disulfides, hindered phenols such as terbutyl catechol, secondary alcohols such as isopropanol, RAFT transfer agents such as trithiocarbonates (especially dibenzytrithiocarbonate), xantates, dithioesters and the like. dithiocarbamates; the addition of monomers other than the residual monomers in a proportion of 0 to 10% of the monomers converted during this step, preferably from 0 to 5%, these monomers being able to be chosen from acrylic acid, methacrylic acid and their esters or amides such as in particular the esters of glycidyl, 2-ethanolamine, polyethylene glycol, 3-propenol, or in particular dimethyl acrylamide. Other monomers such as butadiene, maleic anhydride, vinyl acetate, halogen-functional monomers such as vinyl chloride, vinylidene chloride, vinylidene difluoride, vinyl tetrafluoride can be copolymerized during this synthesis step. The conversion rate of the unconverted monomers can be up to 100% over a period of a few hours (for example, a duration of 4 hours).

The advantageous operating conditions as well as the advantageous characteristics of the products resulting from the fourth step (step 4)) can be the following ones:

monomers used for the synthesis of the second block, chosen from acrylic and methacrylic derivatives, styrene derivatives as defined above; a polymerization temperature greater than 50 ^° C. and less than 200 ^° C., preferably ranging from 90 ^° C. to 175 ^° C.; a conversion achieved, preferably ranging from 45% to 95%, more preferably from 50 to 90%.

The fifth stage takes place under conditions similar to those of the second stage. By way of example, a polymeric material prepared according to the invention is a material comprising a diblock copolymer (n-butyl polyacrylate-b-polymethyl methacrylate).

The process of the invention can be applied to bulk polymerization methods, organic solvent (such as toluene), emulsion, suspension. Each step of the process can be carried out in the same reactor via a "batch" process (or batch process), or in different reactors optionally in semi-continuous or continuous processes.

The invention also relates to a polymeric material obtainable by the method described above, comprising a multiblock copolymer comprising n blocks connected to each other by covalent bond, n being an integer greater than or equal to 2, and for at least each of the (n-1) first blocks, preferably, for each of the n blocks, polymer chains formed of the residual monomers forming part of the corresponding block, said chains having a number average molecular mass less than of the corresponding block and, generally, a polydispersity index greater than that of the corresponding block.

These materials benefit from the physico-chemical properties related to its nanostructuring such as, for example, its transparency, its resistance to cracking or its ability to encapsulate other bodies. Thus, another object of the invention is the use of the material as defined above as a thermoplastic material. Because of its transparency properties and its mechanical properties, such as an excellent impact value, the polymeric material according to the invention therefore finds its application in the field of luminaires, automobiles (to constitute, for example, optical headlights), construction, domestic applications (to constitute, for example, display points). It can also find application in the field of cosmetics. It can be specified that the materials of the invention find their application in all known fields of application of polymethyl methacrylate.

Another object of the invention is the use of the material as defined above as a nanostructuring additive of polymer matrices. Such matrices are for example thermoplastic polymers (polystyrene, polymethyl methacrylate, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyamides, polypropylene, polyethylene, ...), thermosetting polymers (poly epoxides, poly urethanes, unsaturated polyesters. ..), crosslinked matrices (such as rubbers, polyethylenes, crosslinked styrene - butadiene resins) and mixtures thereof. Nanostructuring or nanostructured additives make it possible to to give these matrices improved use properties.

Finally, another subject of the invention is the use of the material as defined above as a reinforcing and / or rheoplasticizing additive of polymer matrices. He therefore finds, as an additive, its application in the field of aeronautics, electricity, electronics, thermostructural adhesives, sports equipment, coatings. Compared to pure block copolymers, the presence in this material of low molecular weight chains will induce better fluidity during the processing steps of these host matrices such as injection and thermoforming.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 represents a photograph obtained by atomic force microscopy of a material of example 3;

FIG. 2 represents a photograph obtained by atomic force microscopy of a material of example 4;

FIG. 3 represents a photograph obtained by atomic force microscopy of a material of example 6. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

For the implementation of the examples below, the initiators of the alkoxyamine type were prepared beforehand, as follows:

The initiator and control agent of the monoalkoxyamine type of the following formula:

This initiator is prepared as follows:

In a nitrogen-purged 2-liter glass reactor, 500 ml degassed toluene, 35.9 g CuBr (250 mmol), 15.9 g copper powder (250 mol), 86.7 g are introduced. N, N, N ', N ^f, N "-pentaméthyl- diethylenetriamine PMDETA- (500 mmol) and then, under stirring and at room temperature (20 ⁰ C) is introduced a mixture containing 500 mL of degassed toluene, 42 1 g of 2-bromo-2-methylpropionic acid (250 mmol) and 78.9 g of nitroxide of formula: 84% or 225 mol.

Allowed to react for 90 min at room temperature and with stirring, and the reaction medium is filtered. The toluene filtrate is washed twice with 1.5 L of saturated aqueous NH ₄ Cl solution.

A yellowish solid is obtained which is washed with pentane to give 51 g of 2-methyl-2- [N-tert-butyl-N- (diethoxyphosphoryl-2,2-dimethylpropyl) aminoxy] propionic acid (60% yield).

The analytical results are given below: mass mass determined by mass spectrometry: 381.44 / g mol ^-1 (for C ₁₇ H ₃₆ NO ₆ P) - elemental analysis (crude formula:

C ₁₇ H ₃₆ NO ₆ P):

% calculated: C = 53.53, H = 9.51, N = 3.67% found: C = 53.57, H = 9.28, N = 3.77 melting on Buchi B-540 apparatus: 124 ⁰ C / 125 ⁰ C

The initiator and dialkoxyamine control agent of the following formula:

This initiator is prepared according to the protocol described in FR 2861394.

The polymeric materials prepared according to the examples set out below are respectively analyzed by:

H-NMR in deuterated chloroform on Brucker 400 apparatus;

- DMA (abbreviation for Dynamic Mechanical Analysis meaning Dynamic Thermal Analysis), which consists in measuring the viscoelastic properties G ', G''and tan δ of a product as a function of the temperature at a stress frequency of 1 Hz, the magnitudes G ', G''and tan δ respectively corresponding to the elastic or conservation modulus (in Pa), to the viscous or loss modulus (in Pa) and to the ratio (G''/G'), these measurements being carried out on a ARES rheometer of Rheometrics Scientific and providing access to the glass transition temperature value of the material; size exclusion chromatography carried out at 30 ^° C. using a polystyrene standard as a reference for measuring the number-average molecular masses.

EXAMPLE 1

This example presents the preparation of a first bulk n-butyl polyacrylate block by a bulk process, which will be used for the following Examples 2 to 5.

The protocol for preparing this first living block is as follows:

In a 16 liter jacketed stainless steel reactor equipped with a decompression valve calibrated at 10 bar and a "double helix" type stirrer, 12 kg of n-butyl acrylate and 150 g of the initiator of the monoalkoxyamine type defined above at room temperature. The mixture is degassed and maintained under 3 bars of nitrogen atmosphere and then heated to reach the temperature of 118 ^° C. The exothermicity of the polymerization reaction is counteracted by means of a brine heat exchanger at (-25 ^° C. ⁰ C). The mixture is heated for 3.5 hours until completion of the polymerization reaction.

The mixture is then cooled to room temperature in 15 minutes so as to quench the reaction mixture. A solution of polymer in n-butyl acrylate is recovered by a bottom valve. A solids measurement indicates that there was a 60% conversion, i.e., 60% of the n-butyl acrylate present in the initial mixture polymerized. The intermediate n-butyl polyacrylate is characterized by size exclusion chromatography, which provides the following data:

Number average molecular weight Mn = 1930 g / mol; Polydispersity index Ip = I, 35.

This polymer solution is used as such for Examples 2 to 5.

Example 2

This example illustrates the preparation of a diblock copolymer by controlled radical polymerization, by a process taking place in mass / organic solvent according to the prior art.

The preparation protocol is as follows:

After cleaning with toluene, the same reactor as in Example 1 is charged with 2.5 kg of the solution obtained in Example 1 and 4 kg of methyl methacrylate, the initial mixture thus comprising 1.5 kg of polyacrylate. of living n-butyl, 1 kg of residual n-butyl acrylate and 4 kg of methyl methacrylate. The whole is diluted with 2.5 kg of toluene. After putting under nitrogen, the reactor is heated to 105 ^° C. for one hour and then at 120 ^° C. for one hour before being cooled in 15 minutes at room temperature. The solids content is 55%, which corresponds to a conversion of the monomers (methyl methacrylate + residual n-butyl acrylate) of 70%.

The diblock copolymer obtained has the following characteristics:

- number average molecular weight Mn = 65000 g / mol;

Polydispersity index Ip = 2.1.

The chemical composition of the copolymer is determined by 1 H NMR and gives the following results: polymethyl methacrylate: 55% (by weight); n-butyl polyacrylate: 45% (by weight);

It also follows from this analysis that the polymethyl methacrylate block comprises 16% by weight of n-butyl acrylate.

Such a copolymer is nanostructured but the analysis by DMA shows that the glass transition temperature of the second block is 95 ^° C., which is 15 ^° C. below that obtained for a pure polymethyl methacrylate. The copolymer of the example can therefore find no application requiring thermal stability beyond 80 ^° C. EXAMPLE 3

This example illustrates the preparation of a polymeric material comprising a diblock copolymer by controlled radical polymerization, by a process taking place in mass / solvent under conditions not in accordance with the invention.

The preparation protocol is as follows:

1 kg of the solution obtained in the example

1 is diluted with 500 g of toluene and then introduced into a jacketed stainless steel 5 liter reactor equipped with a decompression valve calibrated at 10 bar and an anchor type stirrer.

1 g of AiBN is added at room temperature

(bis (azoisobutyronitrile) The mixture is degassed, put under nitrogen, stirred and then heated to 85 ^° C. The temperature is maintained below 95 ^° C. for 2 hours.

The final mixture has a solids content of 65%, ie a conversion of 86% of the residual n-butyl acrylate.

On these two stages, 94.5% acrylate was converted.

The analysis by gas chromatography indicates a number average molecular weight Mn of 28,500 and a polydispersity index Ip of 6.

In the same reactor, 3 kg of methyl methacrylate are added. The mixture is degassed then heated at 105 ^° C. for one hour and then at 120 ^° C. for another hour.

The final conversion is 50% methyl methacrylate. The composition of the product is as follows:

60% of polymethyl methacrylate;

40% of n-butyl polyacrylate, 24% of which is bound to the polymethyl methacrylate block and 16% of n-butyl polyacrylate not bound to the block.

The highest Tg of the product analyzed by DMA is HO ⁰ C, which is a Tg according to the invention. However, it is observed by atomic force microscopy that n-butyl acrylate agglomerates in nodules of the order of several hundred nanometers, which shows that some of the free chains generated during the second step are not soluble in the otherwise nanostructured network of the block copolymer. This organization explains the slight veil observed in the material in Figure 1.

EXAMPLE 4

This example illustrates the preparation of a polymeric material comprising a diblock copolymer by controlled radical polymerization in solution according to the conditions of the invention.

1) Manufacture of the n-butyl polyacrylate block. 1 kg of the solution obtained in the example

1 is introduced into a jacketed stainless steel 5 liter reactor equipped with a decompression valve calibrated at 10 bar and an anchor-type stirrer. 1 g of AiBN is added at room temperature

(bis (azoisobutyronitrile)) and 1.2 g of dodecyl mercaptan. The mixture is degassed, put under nitrogen, stirred and then heated to 85 ^° C. The temperature is maintained below 95 ^° C. for 1 hour. The final mixture has a dry extract of 97.5%.

The analysis by gas chromatography provides the following data:

- Number average molecular weight Mn =

17500;

Polydispersity index Ip = I, 8.

2) Manufacture of the diblock copolymer in solution.

In the same reactor, 3 kg of methyl methacrylate and 500 g of toluene are added. The mixture is degassed and stirred for one hour at ambient temperature, so as to be well homogeneous, then it is heated at 105 ^° C. for one hour and then at 120 ^° C. for another hour.

The final conversion is 55% of methyl methacrylate. The composition of the material in solution is as follows: 62% of polymethyl methacrylate;

38% of n-butyl polyacrylate, including 22.8% of butyl polyacrylate bound to the polymethyl methacrylate block and 15.2% of non-block bound n-butyl polyacrylate.

The highest Tg of the product analyzed by DMA is HO ⁰ C, which is in accordance with the invention. It is observed by atomic force microscopy that, on scales of several microns, the product is well nanostructured. The n-butyl polyacrylate produced in the presence of transfer agent is well soluble in the nanodomains of the block copolymer (see FIG. 2). As expected, the product obtained is very transparent.

3) Manufacture of a material in continuous mass and having good mechanical properties.

5 kg of product obtained as in step 1) are mixed with 30 kg of methyl methacrylate. This mixture is introduced into a storage tank cooled to -20 ^° C.

The solution is injected at a flow rate of 2 kg / h in a 5 liter reactor heated to 155 ⁰ C and with a continuous extraction system feeding a devolatilizing extruder through transfer lines heated at 9O ⁰ C. The extraction rate corresponds to the introduction rate. The flow rate is maintained at this rate until the solid content inside the reactor reaches a value between 50 and 55%. From this moment, the flow rate is adjusted so that the temperature in the reactor is 163 ^° C. ± 5 ^° C. (the flow acceleration serves to lower the temperature, a slowing increases it).

After degassing, transparent granules indicative of nanostructuration are recovered (the transparency index is 98%).

The high Tg of the product analyzed by DMA is 108 ^° C., which is in accordance with the invention.

The mechanical tests of the material show a resilience in the notch impact test of 82 kJ / m ² , a modulus of 1680 MPa, comparable to the values found in the same tests for commercially impacted polymethyl methacrylate grades.

EXAMPLE 5

This example illustrates the preparation of a polymeric material comprising a diblock polymer by controlled radical polymerization in emulsion according to the conditions of the invention.

a) Preparation of the difunctionalized poly (n-butyl) block living in emulsion. The preparation of the living difunctionalized poly (n-butyl acrylate) block by controlled radical polymerization in emulsion is carried out in two stages.

* First step: Preparation of a seed with low solids content (about 1% by weight).

In a 2-liter reactor equipped with a variable speed stirring motor, inputs for the introduction of reagents, taps for the introduction of inert gases to remove oxygen, such as nitrogen, and measurement probes (eg of temperature) of a vapor reflux condensing system, a double jacket for heating / cooling the reactor contents by circulating a coolant therein, introduced 6.6 g (ie 0.05 mol) of n-butyl acrylate, 500 g of distilled water, 3.3 g (4.01 mmol) of emulsifying agent ODwfax 8390, 0.55 g (6, 55 mmol) of NaHCO ₃ and 2.3 g (2.39 mmol) of dialkoxyamine of formula given above, prepared according to what is described in FR 2861394, neutralized with an excess of sodium hydroxide (1.7 equivalents per function acid present in the dialkoxyamine is 0.326 g of NaOH). The reaction mixture is then degassed several times with nitrogen, then heated to 120 ^° C. and this temperature is maintained by thermal regulation for 8 hours. * Second step: Addition of n-butyl acrylate.

To the seed prepared in the first step, 143.4 g (1.12 mol) of n-butyl acrylate are introduced in one go. The reaction medium is then degassed several times with nitrogen, stirred at room temperature for 30 minutes, then heated to 120 ^° C. This temperature is maintained by thermal regulation for about 1H30, until the conversion of the acrylate n-butyl reaches 80%.

Samples of the reaction medium are taken every hour to determine the kinetics of gravimetric polymerization (measurement of dry extracts). The solids content of the difunctionalized poly (n-butyl acrylate) latex obtained is about 18%.

The conversion of n-butyl acrylate is evaluated at 80% by weight by gravimetry. The molecular weights of the difunctionalized poly (n-butyl acrylate) obtained by Radical Polymerization Controlled in Polystyrene Equivalent are as follows:

Peak molecular weight Mw = 50,000 g / mol;

Number average molecular weight Mn = 45,000 g / mol;

Mass-average molecular weight Mw = 68,000 g / mol. Polydispersity index Ip = 1.5. b) Baking of the residual n-butyl acrylate in emulsion.

With the poly (n-butyl acrylate) latex prepared beforehand, a solution containing 0.225 g (0.83 mmol) of ammonium persulfate, 0.219 g (1.42 mmol) of formaldehyde sulphoxylate, is then added all at once. sodium and 0.045 g (0.22 mmol) of t-dodecyl mercaptan transfer agent in 5 mL of distilled water to convert the remaining 20% n-butyl acrylate. The reaction medium is degassed and then heated at 60 ^° C. (temperature below the dissociation temperature of the difunctionalized poly (n-butyl acrylate) for 4 hours). The solids content of the poly (n-butyl acrylate) latex obtained is 22%.

The conversion of n-butyl acrylate is then evaluated at 98% by weight by gravimetry. The molecular weights of poly (n-butyl acrylate) obtained by controlled radical polymerization and conventional radical polymerization in polystyrene equivalents are as follows:

Molecular weight at peak Mw = 46000 g / mol;

Number average molecular weight Mn = 36000 g / mol;

Mass-average molecular weight Mw = 72500 g / mol. Polydispersity index Ip = 2. c) Reinstatement of the poly (n-butyl acrylate) block difunctionalized with methyl methacrylate.

It is added to the preceding latex (containing the difunctionalized poly (n-butyl acrylate) and the poly (n-butyl acrylate) resulting from the conventional radical polymerization process) at room temperature, 6.2 g (7.54 mmol). Dowfax 8390 emulsifier, 490 g of distilled water and 0.54 g (6.43 mmol) of NaHCC> ₃ . After degassing with nitrogen, the reaction medium is brought to 105 ^° C., and when the temperature reaches 105 ^° C., 280 g (2.80 mol) of methyl methacrylate are then added continuously over a period of 3 hours. The temperature is then maintained at 105 ^° C. for three additional hours and then the reaction medium is cooled to ambient temperature. The conversion of methyl methacrylate is evaluated by measuring 35% solids content.

The solids content of the latex is 17%. The residual methyl methacrylate is then converted by a conventional radical polymerization process as described in the step below.

d) Baking of the residual methyl methacrylate by a conventional radical emulsion polymerization process.

After cooling of the above latex, a solution containing 0.364 g (1.35 mmol) of potassium persulfate in 5 ml of distilled water is introduced at ambient temperature. The environment The reaction mixture is degassed with nitrogen then heated to 75 ^° C. and maintained at this temperature for 4 hours. The conversion of methyl methacrylate is then evaluated at 98% by measurement of dry extract.

The solids content of the latex obtained is 30%.

EXAMPLE 6

The product obtained in Example 5 is dissolved at a rate of 10% by weight in a mixture

DGEBA / MDEA at a temperature of 95 ^° C., of respective formulas:

After degassing, the crosslinking reaction is initiated at 135 ^° C. and the cooking is continued for 2 hours.

After baking, the thermoset material is transparent. Transmission electron microscopy analysis reveals that this material is nanostructured. The copolymer is dispersed in the form of particles clear, surrounded by a dark crown of irregular thickness, shape and variable sizes. These domains are of the order of 10 nm. The core is butyl polyacrylate, the bark is the butyl polymethacrylate domains, which have good affinity with the epoxy matrix (see Figure 3).

Claims

A process for preparing a polymeric material comprising a multiblock copolymer comprising n blocks, where n is an integer greater than or equal to 2, said method comprising at least one cycle of steps comprising: a) a step of synthesizing a block by controlled radical polymerization of one or more radically polymerizable monomers; b) a step of polymerizing said unconverted monomers in step a) into a polymer having a number average molecular weight less than the number average molecular weight of said block; said cycle of steps being performed at least for the (n-1) first blocks.

The method of claim 1, wherein the step cycle is performed for the n blocks.

3. Process for the preparation of a polymeric material comprising a copolymer comprising at least one block A and at least one block B, said process comprising successively: 1) a step of polymerization of one or more monomers that can be polymerized radically by radical polymerization controlled, to form block A;

2) a step of polymerization of the monomer or monomers not converted during step 1), to form a polymer of chemical nature identical to the block A but of lower average molecular weight than that of block A;

3) a step of adding to the medium resulting from steps 1) and 2) of one or more radical-polymerizable monomers precursors of block B;

5) optionally a step of polymerization of the monomer or monomers not converted during step 4), to form a polymer of chemical nature identical to block B but of number average molecular weight less than that of block B.

4. Process according to any one of the preceding claims, carried out in emulsion, in bulk, in organic solvent.

5. Method according to any one of the preceding claims, wherein each step a) or steps 1) and 4) is (are) implemented by SFRP polymerization.

6. Process according to claim 5, in which the SFRP polymerization is carried out in the presence of at least one alkoxyamine chosen from the monoalkoxyamines of formula (I): Ri C (CH ₃ ) ₃

R ₃ -CON CH-C (CH ₃ ) ₃

C (O) OR ₂ P (O) (OEt) ₂

(D in which:

R.2 represents a hydrogen atom, an alkali metal, an ammonium ion, a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 8, a phenyl group.

The process according to claim 6, wherein the alkoxyamine has the following formula:

8. Process according to claim 5, in which the SFRP polymerization is carried out in the presence of at least one polyalkoxyamine resulting from a process consisting of reacting one or more alkoxyamines of formula (I) below: Ri C (CH ₃ ) ₃

R ₃ -CON CH-C (CH ₃ ) ₃

C (O) OR ₂ P (O) (OEt) ₂

(D in which:

R ₂ represents a hydrogen atom, a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 8, a phenyl group, an alkali metal, an ammonium ion; with at least one polyunsaturated compound of formula (II):

(II) wherein Z represents an aryl group or a group of formula in which Zi represents a polyfunctional structure, X is an oxygen atom, a nitrogen atom carrying a carbon group or an oxygen atom, a sulfur atom and n is an integer greater than or equal to 2, in the presence or absence of solvent (s), at a temperature ranging, in general, from 0 to 90 ^° C., the molar ratio between monalcoxyamine (s) of formula (I) and polyunsaturated compound (s) of formula (I) II) ranging from 1.5 to 1.5n; this step possibly being followed by a step of evaporation of the possible solvent (s).

The process according to claim 8, wherein the polyalkoxyamine has the following formula:

10. Process according to any one of claims 6 to 9, wherein the alkoxyamine or polyalkoxyamine is introduced into the polymerization medium at a rate of 0.01% to 10% by weight relative to the mass of monomer (s). ).

11. Process according to any one of the preceding claims, in which the radical-polymerizable monomer or monomers are chosen from monomers having a carbon-carbon double bond capable of radical polymerization.

12. The method of claim 11, wherein the monomers having a carbon-carbon double bond capable of radical polymerization are chosen from vinylaromatic monomers, dienes, acrylic monomers, alkyl acrylates, cycloalkyl acrylates or alkyl acrylates. aryl, hydroxyalkyl acrylates, alkyl ether acrylates, alkoxy- or aryloxy-polyalkylene glycol acrylates, ethoxypolyethylene glycol acrylates, methoxypolypropylene glycol acrylates, methoxy-polyethylene glycol-polypropylene glycol acrylates or mixtures thereof, acrylates aminoalkyl, amino salt acrylates, fluorinated acrylates, silyl acrylates, phosphorus acrylates, methacrylic monomers, alkyl, cycloalkyl, alkenyl or aryl methacrylates, hydroxyalkyl methacrylates , ether alkyl methacrylates, alkoxy or aryloxy polyalkylene glycol methacrylates, methacrylates of aminoalkyl, amino salt methacrylates, fluorinated methacrylates, silyl methacrylates, phosphorus methacrylates, hydroxyethylimidazolidone methacrylate, hydroxyethylimidazolidinone methacrylate, 2- (2-oxo-1-imidazolidinyl) ethyl methacrylate, Acrylonitrile, acrylamide or substituted acrylamides, 4-acryloylmorpholine, N-methylolacrylamide, acrylamidopropyltrimethylammonium chloride (APTAC), acrylamidomethylpropanesulfonic acid (AMPS) or its salts, methacrylamide or substituted methacrylamides, N-methylolmethacrylamide, methacrylamidopropyltrimethylammonium (MAPTAC), itaconic acid, maleic acid or its salts, maleic anhydride, alkyl or alkoxy- or aryloxy-polyalkyleneglycol maleates or maleates, vinylpyridine, vinylpyrrolidinone, (alkoxy) poly (alkylene glycol) vinyl ether or divinyl ether, poly (ethylene glycol) divinyl ether, olefinic monomers, fluorinated olefinic monomers, vinylidene monomers, alone or as a mixture of at least two monomers mentioned above.

13. Process according to any one of the preceding claims, in which each step a) or steps 1) and 4) are carried out, when the process is carried out in emulsion, in the presence of at least one anionic emulsifying agent. cationic or nonionic.

The process according to claim 13, wherein the emulsifier is selected from alkyl or aryl sulfates, alkyl or aryl sulfonates, fatty acid salts, polyvinyl alcohols, alcohols, and the like. polyethoxylated fats.

15. Process according to any one of the preceding claims, in which each step b) or steps 2) and 5) are carried out in the presence of a radical polymerization initiator chosen from peroxidic compounds, persulfate compounds, azo compounds, redox compounds.

16. Process according to any one of the preceding claims, in which each step b) or steps 2) and 5) are carried out at a polymerization temperature that is at least 20 ^° C. lower than that of each step a) or steps 1) and 4).

17. Process according to any one of the preceding claims, in which each step b) or steps 2) and 5) are carried out in the presence of at least one transfer agent chosen from sulfur compounds, alcohol compounds, transfer agents used for radical polymerization of the RAFT type.

18. The method of claim 17, wherein the sulfur compounds are selected from mercaptan compounds comprising at least 4 carbon atoms, the disulfide compounds.

19. The method of claim 17, wherein the alcohol compounds are selected from hindered phenols, secondary alcohols.

20. Process according to claim 17, in which the transfer agents used for radical polymerization of the RAFT type are chosen from trithiocarbonates, xanthates, dithioesters and dithiocarbamates.

21. A method according to any one of the preceding claims, wherein the material polymer is a material comprising a diblock copolymer.

22. The process according to claim 21, wherein the diblock copolymer is a copolymer

(n-butyl polyacrylate-b-polymethylmethacrylate).

23. A polymeric material obtainable by a process as defined in any one of the preceding claims, comprising a multiblock copolymer comprising n blocks connected to each other by covalent bond, n being an integer greater than or equal to 2, and for at least each of the (n-1) first blocks, polymer chains formed of the residual monomers forming part of the corresponding block, said chains having a number average molecular weight less than that of the corresponding block.

24. polymeric material according to claim 23, comprising polymer chains formed of the residual monomers forming part of the constitution of the corresponding block, said chains having a number average molecular weight less than that of the corresponding block for each of the n blocks.

25. Use of a material as defined in claim 23 or 24 as a thermoplastic material.

26. Use according to claim 25, wherein the material is applied to the field of lighting, automotive, construction, domestic applications, cosmetics.

27. Use of a material as defined in claim 23 or 24 as a nanostructuring additive of polymer matrices.

28. Use of a material as defined in claim 23 or 24 as a reinforcing additive and / or rheoplasticizer of polymer matrices.

29. Use according to claim 28, wherein the material is applied to the field of aeronautics, electricity, electronics, thermostructural adhesives, sports equipment, coatings.